1. Field of the Invention
The present invention generally relates to a connector and a manufacturing method thereof, and more specifically, to a balanced transmission connector and a manufacturing method thereof.
2. Description of the Related Art
Conventionally, as connector devices for electrically connecting a motherboard and a backplane, there have been known a plug connector and a jack connector. The plug connector and jack connector are provided with plural pairs of signal contacts for transmitting signals having a waveform that is symmetrical about the horizontal axis (positive negative symmetrical waveform), and with plural ground contacts arranged one by one between the adjacent pairs of signal contacts (for example, see Patent Document 1). With this configuration, crosstalk caused between the adjacent pairs of signal contacts can be prevented, and signals can be transmitted at high speed.
[Patent Document 1] Japanese Patent Application Publication No. 2005-100994
A balanced transmission connector disclosed in Patent Document 1 has an insulator for supporting the plural signal contacts and plural ground contacts to be mutually insulated from each other. The insulator includes plural fixing holes each having a linear-shaped cross section. The plural signal contacts and plural ground contacts each having a linear-shaped cross section (plate shape) are pressed to be fixed into the fixing holes. This insulator is formed by molding resin by using a mold. On a bottom surface of the mold, plural protrusions having the linear-shaped cross sections are implanted in order to mold the plural fixing holes having the linear-shaped cross sections in resin.
To arrange the plural contacts at a high density in this balanced transmission connector, the contacts are formed thin. Therefore, the protrusions used for molding the fixing holes in the resin are formed thin as well. As a result, strength of a part of the mold, which is used for molding the fixing holes in the resin, is decreased. Thus, the quality of the insulator has not been stabilized in some cases. In particular, the fixing holes for the signal contacts are smaller (normally, half or less) in size than the fixing holes for the ground contacts. Therefore, the strength of a part of the mold, which is used for molding the fixing holes for the signal contacts in the resin, is degraded.
In view of the above-described circumstances, a configuration in which each of the fixing holes for the signal contacts is formed to have a T-shaped cross section has conventionally been suggested. According to this configuration, the fixing holes for the signal contacts are molded in the resin by using protrusions having the T-shaped cross sections. Therefore, strength of a part of the mold, which is used for molding the fixing holes for the signal contacts in the resin, can be increased. Consequently, the quality of the insulator can be stabilized. Moreover, according to this configuration, there is a space between the signal contact and the ground contact. Therefore, the dielectric constant (relative dielectric constant) between the signal contact and the ground contact can be reduced. Accordingly, impedance can be increased.
In this configuration, however, the signal contacts having the linear-shaped cross sections (plate shapes) are pressed into the fixing holes for the signal contacts, which have T-shaped cross sections. Therefore, there are cases where the signal contacts are axially rotated and thus the distance between the signal contact and the ground contact is changed. Accordingly, there have been cases where the impedance is changed and the impedance match is degraded.